I had an extensive 6x9 listening test at the local Fry's store.
There were Polk, Infinity, Pioneer and MB Quart on display.
Although it is not the good place to do the listening test, at least I could do direct comparision on different models side by side. I understood that all of the speakers didn't go through the break in period.

Though I wasn't happy with all of them, at least I found the top of the line Polk 6x9 to be more suitable for my musical taste.
They seem to have strong but tight bass extension, yet less forward'n harshy on mids and highs. Overall, I find them to be less fatiguing in a long term listening situation. Again, as you may all know, these speakers didn't go through extensive break in period so the true representations might be wrong.
Unfortunately, they didn't have the Alpine on display.

If you were to choose from Alpine SPR-69C vs. Polk MMC690, which pairs would you get?
I've heard about the Focal. But I wasn't thrilled with their cost saving polyglass speaker basket. I prefer solid heavy meta that could supress the vibrationl. However, I'm opened to suggestions if there is a better pair of 6x9 out there. I'm thinking about $200+ range.

I'm more into classical, fusion jazz and the 80's than the what most teenagers are listening to these days. I prefer clear and transparent transient than boomy sounds. Also, it's very critical that the highs and mids to be less forwarding, hence more blending into the front seat speaker set. Some young people like cut through vocals, guitars and boomy bass but I'd rather have them blend into the stage.

I'm running a pair of Dynaudio in the front. You may all know that these pairs are known for smooth, non-fatiguing sounds.
I don't intend to run a sub. So I hope that the 6x9 would have decent punchy bass that could somewhat suppliment the missing link. I know I'm asking too much for a pair of 6x9.
Your hands on experience is greatly appreciated.